Cigarette paper



United States PatentO 2,738,791 7, CIGARETTE PAPER Milton 0. Schur, Asheville, and Robert M. Levy, Brevard,

N. C., assignors to' Ecusta Paper Corporation, a corporation of Delaware I N Drawing. Application August 30, 1951, Serial No. 244,475

7 Claims. c1. 131-15 This invention relates to cigarette paper made from wood fibers and more particularly to an improved process of manufacture of same, whereby the formation and the watermarking characteristics of the paper are substan tially improved and simulate the characteristics heretofore obtained in cigarette paper made from bast fiber, such as flax.

The improvement that characterizes the present invention is obtained principally by incorporating in the paper furnish a chemical compound that reverses the sign of the electrical charge, i. e., electrokinetic potential, on the carbonate filler component of the paper furnish so that its tendency to agglomerate with the cellulose fibers in the suspension of the furnish in water and thereby produce a cigarette paper having a wild or mottled appearance, is greatly reduced.

The carbonate filler, such as, for example, calcium carbonate, that is 'commonlyused in cigarette paper to regulate the porosity and burning rate of the paper, normally has a positive electrical charge when suspended'in water, whereas the cellulose fibers, whether they be bast fibers or wood fibers, normally have a negative charge when suspended in water. These particles of opposite charge are attracted to each otherand thereby tend to produce a clotting or flocculating of fiber and filler particles which results in a cigarette paper sheet of nonuniform formation or appearance.

, 2,738,791 Patented Mar. 20, 1956 2 the same negative charge. In this manner a substantially improved distribution of filler and fiber particles is obtained in the furnish and in the resulting cigarette paper sheet, and the final product is so improved over the wood 7 fiber cigarette paper made heretofore that it can be sold corporated in the carbonate filler or in the paper furnish This efiect is especially noticeable in the so-called com- 7 bustible type of cigarette paper that contains about 20% to 30% calcium carbonate filler based on the total weight of the paper, and which will burn after puffing of the cigarette is discontinued. combustible type, that is, if it will not continue to burn when puifing of the cigarette is discontinued, it will contain smaller percentages of filler such as 8% to 15%, but the clotting eifect may still .be apparent. i

In addition to the formation characteristic of the cigarette paper, it is usually important that the paper have'a clearly defined watermark, that is, the fine parallel lines which characterize'most commercial cigarette paper today and which are produced by the use of a dandy roll on the cigarette paper-making machine. Unless there is good uniform distribution of the fiber and filler'compo- :nents in .the cigarette paper furnish, the dandy roll marking will not befine and clear-cut, in the same way that .the formation of the paper will not be uniform.

In accordance with the present invention, we have discovered a method and means of obtaining the desired uniform formation andfine watermarking characteristics in cigarette paper made from wood fibers, so that they :approach, if not attain, the characteristics of Hair or'similar bast fiber cigarette paper of relatively uniform formation. We have found that by incorporating in the furnish a suitably small amount of a soluble polyphosphate, or equivalent sign-reversing compound, the normally positive charge on the carbonate filler will be changed to a negative. charge and the filler particles will thus be repelled rather than attracted by the fiber particles which have If the paperis of the semicontaining both the carbonate filler and the wood fibers, a substantial improvement in the dispersion or deflocculation of the stock is immediately apparent. The wood pulp fibers and carbonate filler no longer tend to flocculate in the head box or on the paper-forming wire of the paper machine, or have a greatly reduced tendency to flocculate, and the cigarette paper sheeted from this stock and dried in conventional manner on the paper machine presents a nice, uniform formation and watermark and is a distinct improvement over the relatively wild formation which ordinarily characterizes wood fiber cigarette paper.

In addition to the substantial and important improvement in formation and watermark characteristics of the wood fiber cigarette paper obtained by the use of a signreversing agent as described above, these characteristics of the final cigarette paper sheet may be further improved, if desired, by the incorporation in the paper furnish of a suitable gum, such as deacetylated karaya gum or other polyose gum. A Although there is no apparent'interreaction between the gum and the charge-reversing agent above described, there is an interdependent relationship which is demonstrated by the fact that if the charge-reversing agent were not used and the gum were added to the pulp, the furnish would clot badly and would result in a paper of exceedingly wild formationi In fact, the clotting of the furnish is in some instances so pronounced as to clog the screens at the head of the paper machine.

On the other hand, when a charge-reversing agent, such as, for example, tetras odium pyrophosphate, isused, it prevents the filler from agglomerating with the cellulose fibers and the addition of the gum no longer clots the furnish, but, on the contrary, aids in effecting the improved distribution of the filler'and fiber particles and in the production of a final cigaretteipaper sheet having good formation and watermark characteristics. In-this man ner, the addition of a gum to the furnish may be employed to augment the improvement which is obtained by reversing the charge on the filler. I

The filler most commonly used in commercial cigarette paper today is precipitated calcium carbonate. However, other fillers, such as magnesium carbonate, the reaction products of carbon dioxide with dolomitic lime, or various mixtures of fillers of this type might be employed as the filler, and the improvements of the present invention would be obtained when such a filler or mixture of fillers were used.

Typical but non-limiting examples of the process are as follows:

Example I millimeter and to a Schopper-Riegler freeness of about stock entered the screen, there was added to it a 1% 1 aqueous solution of partially deacetylated karaya gum. The .rate of addition of the gum solution was equivalent to 0.1% karaya gum based on the weight of the paper being made, both on a dry basis. The cigarette paper as it came off the dry end of the machine weighed 20 grams per square meter and contained 26% calcium carbonate filler, basedon the .dry weight of the paper. It was excellent in all its properties, including clarity of the watermark and uniformity of formation.

Example II For purposes of comparison, the pulp was run over the paper machine without the addition of deacetylated karaya gum to the fiber or tetrasodium pyrophosphate to the filler, and a sheet weighting 20 grams per square meter and containing 26% filler was produced. The strength and porosity characteristics of the paper were practically identical with those of the previous run, but the watermark was relatively blotchy in appearance and the formation distinctly mottled.

Example III In another example, the wood pulp was run over the paper machine without the addition of deacetylated karaya gum, but the filler was treated with tetrasodium pyrophosphate as in the first example of procedure. In comparison with the second run, an improved watermark and a markedly improved formation were realized. However, the watermark and formation were not quite as good as in the case of the first run.

Example IV In another series of runs, a l2-gram sheet was made containing 19% filler. In this case, the fiber was shortened to appreciably less than one millimeter and was beaten to an appreciably lower freeness, since such modifications are necessary when the paper is exceedingly light in weight. In this case, the use of tetrasodium pyrophosphate alone improved the watermark and formation to an important extent.

The use of the polyphosphates or other sign-reversing reagents is usually associated with a lesser retention of filler on the paper machine. Ordinarily, the filler retention may run about 75%. In the case of the runs described above, the normal retention in the presence of soluble polyphosphate would be nearer 68%. This loss is compensated for by the addition of extra filler.

The amount of tetrasodium polyphosphate or similar charge-reversing agent that may be used in accordance with our invention is about 0.1% to 1% based on the weight of the filler. The percentage will vary with different furnishes, with manufacturing conditions and equipment, and with the degree of defiocculation required. in actual practice we have found that the use of more than 1% is of no advantage, and, accordingly, the 1% is an economically desirable upper limit.

Regarding the gum which may be used, such as, for example, the deacetylated karaya gum, we have found that under some conditions an amount as small as 0.01% based on the total weight or". paper gives appreciable improvement, and that as high as 1% to 2% of the gum may be used for obtaining the desired improvement in fiber distribution, and the percentage will depend largely upon the place and conditions under which the gum 1s incorporated. The gum is very sensitive 'to agitation and if it is added to the furnish, for example, in the machine chest and then is subjected to the pulp refining operations normally carried out between the machine chest and the head box of the paper machine, a considerably larger amount-of gum is required, such as 1% to 2%. For this reason, it is usually desirable to add the gum after these refining operations, that is, at the head box of the paper machine where a substantially small amount, such as, for example, 0.1%, is sulficient to give the added improvement above described.

The invention has been described hereinabove with particular reference to cigarette paper made from wood pulp which has inherently a greater tendency to produce a sheet of wild or mottled formation than cigarette paper made from bast fibers, such as, flax. In fact, the flax fiber cigarette paper under usual manufacturing conditions has a sufficiently uniform formation or appearance to adverse manufacturing conditions the formation characteristic of flax cigarette paper will sometimes fall below the desired high quality and when this occurs, the formation can be substantially improved by incorporating in the bast fiber positively charged filler pulp, a sign-reversing chemical such as the soluble polyphosphates described above. Thus, the process of this invention may be applied to bast fiber cigarette paper, as well as wood fiber cigarette paper, Where desired, as indicated in the appended claims.

This application is a continuation-in-part of our copending application Serial No. 181,920, filed August 28,. 1950.

We claim:

1. A cigarette paper having improved formation and watermark characteristics, containing wood pulp fibers, approximately 8% to 30% calcium carbonate filler and approximately 0.1% to 1%, based on the weight of dry filler, of tetrasodium pyrophosphate.

2. A cigarette paper having improved formation and watermark characteristics, containing wood pul fibers, carbonate filler and approximately 0.1% to 1%, based on the weight of dry filler, of a charge-reversing agent that changes the normally positive electrical charge on the filler to a negative charge, so that the thus changed negatively charged filler particles will have lessened tendency to agglomerate with the wood fibers and thereby provide more uniform distribution of filler and fiber particles in the cigarette paper sheet.

3. A cigarette paper having improved formation and watermark characteristics, containing wood pulp fibers, carbonate filler, approximately 0.1% to 1%, based on the weight of dry filler, of a charge-reversing agent that changes the normally positive electrical charge on the filler to a negative charge so that the thus changed negatively charged filler particles will have lessened tendency to agglomerate with the Wood fibers and thereby provide more uniform distribution of filler and fiber particles in the cigarette paper sheet, and 0.01% to 2% of a polyose gum that disperses the wood fibers.

4. A cigarette paper having improved formation characteristics and composed of negatively charged cellulosic fibers, a normally positively charged carbonate filler, and the reaction product of said filler and about 0.1% to 1%, based on the weight of dry filler, of a sign-reversing soluble polyphosphate that changes the sign of said filler and effects a negative charge thereon.

5. A cigarette paper having improved formation characteristics and composed of negatively charged bast fibers, a normally positively charged carbonate filler, and the reaction product of said filler and about 0.1% to 1%, based on the weight of dry filler, of a sign-reversing soluble polyphosphate that changes the sign of said filler and effects a negative charge thereon.

6. A cigarette paper having improved formation characteristics and composed of-negatively charged flax fibers, a normally positively charged carbonate filler, and the reaction product of said filler and about 0.1% to 1%, based on the weight of dry filler, of a sign-reversing soluble polyphosphate that changes the sign of said filler and efiects a negative charge thereon.

7. A cigarette paper having improved formation and watermark characteristics, containing cellulosic fibers, carbonate filler and approximately 0.1% to 1%, based on the weight of dry filler, of a charge-reversing agent that changes the normally positive electrical charge on the filler to a negative charge, so that the thus changed negatively charged filler particles will have lessened tendency to agglomerate with the cellulosic fibers and thereby provide more uniform distribution of filler and fiber particles in the cigarette paper sheet.

Erspamer, P 321-326.

Rafton May 5, 1931 Rafton May 5, 1931 Bicknell June 15, 1943 Schur et a1. Ian. 1, 1952 FOREIGN PATENTS Great Britain Nov. 15, 1950 OTHER REFERENCES aper Trade Journal, June 13, 1940, pp. 

1. A CIGARETTE PAPER HAVING IMPROVED FORMATION AND WATERMARK CHARACTERISTICS, CONTAINING WOOD PULP FIBERS, APPROXIMATELY 8% TO 30%, CALCIUM CARBONATE FILLER AND APPROXIMATELY 0.1% TO 1%, BASED ON THE WEIGHT OF DRY FILLER, OF TETRASODIUM PYROPHOSPHATE. 